Increasing demand for more powerful and convenient data and information communication has spawned a number of advancements in communications technologies. One area of particular interest is broadband communication, and related applications. The growing usage of broadband communications has given rise to a number of manufacturing and operational considerations. Some of those considerations are unique to broadband, while others are common to most communications technologies. Amongst the common considerations for most modern communications technologies is the need or desire to maximize data transfer rates.
An emerging trend in broadband communications—especially among technologies such as wireless broadband (WiBro) and TD-SCDMA (Time Division Synchronous Code Division Multiple Access)—is the inclusion of time division duplexing (TDD) operation in systems having relatively high power operations.
Generally, TDD uses a single channel for full duplex communications. Separation between transmit and receive occurs in the time domain on the same carrier frequency. Transmission direction alternates between uplink (i.e., transmit) and downlink (i.e., receive), and the amount of bandwidth allocated to each direction is flexible. A carrier can use any part of the channel to its full capacity in either the forward or reverse direction in response to demand.
TDD-based wireless base-stations and equipment frequently employ a single antenna architecture, utilizing some form of time duplexer module to alternately route the transmitter and receiver to an antenna. Commonly, time duplexer modules take the form of a T/R (transmit/receive) or transceiver switch module—one that simply rapidly switches the antenna connection alternately between transmit and receive channels.
Conventionally, T/R switches have some finite isolation between transmit and receive paths. As such, noise from the transmit channel—especially from components intended to boost transmission signal power (e.g., power amplifier)—may still leak into the receive channel during receive mode, desensitizing or otherwise degrading receiver performance. This is especially problematic for receiver components designed for low-noise operation.
In a number of conventional TDD applications, designers often made a tradeoff between increasing isolation—which was costly from a design and operational overhead perspective—and accepting a certain level of transmission channel noise during receive operation. Such a tradeoff was acceptable in many conventional TDD applications, since the magnitude of the transmission channel noise was relatively small due to relatively low overall system power levels.
With the advent and growth of higher power TDD-based systems, however, the deleterious effects of transmission channel noise during receive operation can no longer be adequately addressed with such conventional tradeoffs. Higher transmission power requirements require greater amplification along the transmission channel—increasing the capacity for and magnitude of noise experienced during receive operation. Greatly increasing isolation circuitry between the transmit and receive channels is costly, and therefore not a practical solution for many cost-sensitive consumer product applications—especially wireless communications systems.
As a result, there is a need for a system that addresses and minimizes the deleterious effects of transmission channel noise during the receive mode of a transceiver component in a high power TDD wireless communications system—in a manner that complements any existing component isolation without requiring increased switch isolation circuitry—providing efficient and reliable communications in an easy, cost-effective manner.